Battery-powered appliances have become ubiquitous. In some instances, it is desirable to know when the end of the life of a battery(s) being used in a battery-powered appliance is approaching. For example, when using a battery-powered computer such as a laptop it is often useful to know when the end of the life of the battery is nearing so that a suitable measure can be taken. Examples of such measures include saving files, closing applications, powering down the system, providing external power, charging the battery, as well as other measures. Such measures may be manually or automatically performed. Some battery-powered appliances, such as laptops, may provide a visual indication of a remaining life of the battery and/or an audible indication when the estimated remaining life of the battery falls below a warning threshold.
Various approaches have been used to estimate the remaining life of a battery being used in a battery-powered appliance. Such approaches have been based on a closed circuit voltage (CCV), an open circuit voltage (OCV), impedance, change in current over time, change in voltage over time, and/or capacity removed during discharge (coulomb counting). Unfortunately, there are many factors that affect battery discharge behavior. For instance, battery temperature, discharge rate, discharge mode (current, power or load), discharge intermittency, cell-to-cell variation, initial charge state of the battery, discharge characteristics, temperature change during discharge, battery chemistry, as well as other factors. The above-noted approaches generally are not well suited for one or more of these factors, particularly with respect to certain primary battery chemistries such as Li/FeS2. As a consequence, these approaches have been known to overestimate or underestimate the remaining life of a battery to a functional endpoint. Thus, in some instances a battery-powered appliance may turn off prior to any measure being taken, while in other instances, such measures may be prematurely performed.
In view of the above, there is an unresolved need for a battery end of life determiner that addresses the above and/or other factors.